How to estimate big numbers (simple tricks that work)
Thousand, million, billion: the words sound close, but the gaps are huge. A million seconds is about 11.5 days. A billion seconds is about 32 years. Here is how to make good guesses anyway.
1. Think in powers of ten
First decide the size class. Is the answer in the hundreds, thousands or millions? Getting the right power of ten is the most important step. In Number Dial, a guess in the right power of ten is already “warm”.
2. Break the question into parts
This is called a Fermi estimate, after the physicist Enrico Fermi. To guess the minutes in a week, multiply 60 minutes by 24 hours by 7 days. You get 10,080. Each step is easy, and the errors often cancel out.
3. Keep anchor numbers in your head
- World population: about 8.2 billion
- Earth’s equator: about 40,000 km
- Seconds in a day: 86,400
- Height of Everest: about 8.8 km
Anchors let you compare instead of guessing from nothing.
4. Use the hints
When you hear “higher”, do not just add a little. If you were cold, jump by a factor of ten. If you were warm, move by about two times. If you were hot, adjust by a quarter or less.
5. Accept being roughly right
A good estimate is within a factor of two. That is often all you need to check a news headline or a price.
Practise with today’s Number Dial question.